`None` in `rustc_mir_build/src/builder/matches/mod.rs`

[cushionbadak]

Code

#![feature(never_patterns)]
#![allow(incomplete_features)]

fn by_value(s: usize) {
    || { let ! = s; };
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.86.0-nightly (6171d944a 2025-02-10)
binary: rustc
commit-hash: 6171d944aea415a3023d4262e0895aa3b18c771f
commit-date: 2025-02-10
host: x86_64-apple-darwin
release: 1.86.0-nightly
LLVM version: 19.1.7

Error output

Command: rustc --edition=2021

This also ICEs with --edition=2024

error: mismatched types
 --> other.rs:5:14
  |
5 |     || { let ! = s; };
  |              ^ a never pattern must be used on an uninhabited type
  |
  = note: the matched value is of type `usize`


thread 'rustc' panicked at compiler/rustc_mir_build/src/builder/matches/mod.rs:2099:44:
called `Option::unwrap()` on a `None` value

Backtrace

thread 'rustc' panicked at compiler/rustc_mir_build/src/builder/matches/mod.rs:2099:44:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: core::option::unwrap_failed
   4: <rustc_mir_build::builder::Builder>::match_candidates_inner
   5: <rustc_mir_build::builder::Builder>::lower_match_tree
   6: <rustc_mir_build::builder::Builder>::place_into_pattern
   7: <rustc_mir_build::builder::Builder>::ast_block_stmts
   8: <rustc_mir_build::builder::Builder>::in_scope::<<rustc_mir_build::builder::Builder>::ast_block::{closure#0}, ()>
   9: <rustc_mir_build::builder::Builder>::expr_into_dest
  10: <rustc_mir_build::builder::Builder>::as_temp_inner
  11: <rustc_mir_build::builder::Builder>::expr_into_dest
  12: <rustc_mir_build::builder::Builder>::expr_into_dest::{closure#0}
  13: <rustc_mir_build::builder::Builder>::expr_into_dest
  14: rustc_mir_build::builder::construct_fn
  15: rustc_mir_build::builder::build_mir
  16: rustc_mir_transform::mir_built
      [... omitted 1 frame ...]
  17: <rustc_mir_build::check_unsafety::UnsafetyVisitor>::visit_inner_body
  18: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  19: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  20: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_block
  21: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  22: <rustc_mir_build::check_unsafety::UnsafetyVisitor as rustc_middle::thir::visit::Visitor>::visit_expr
  23: rustc_mir_build::check_unsafety::check_unsafety
      [... omitted 1 frame ...]
  24: <rustc_middle::hir::map::Map>::par_body_owners::<rustc_interface::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
  25: rustc_interface::passes::run_required_analyses
  26: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  27: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  28: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: please make sure that you have updated to the latest nightly

note: please attach the file at `/Volumes/T7/workspace/250203 scratch/closerable_정리/scratch/rustc-ice-2025-02-11T06_30_38-34940.txt` to your bug report

query stack during panic:
#0 [mir_built] building MIR for `by_value::{closure#0}`
#1 [check_unsafety] unsafety-checking `by_value`
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 1 previous error

Notes

• ICE location: compiler/rustc_mir_build/src/builder/matches/mod.rs Line-2099
  

  rust/compiler/rustc_mir_build/src/builder/matches/mod.rs

  Lines 2094 to 2103 in 6171d94

  	fn pick_test(&mut self, candidates: &[&mut Candidate<'tcx>]) -> (Place<'tcx>, Test<'tcx>) {
  	// Extract the match-pair from the highest priority candidate
  	let match_pair = &candidates[0].match_pairs[0];
  	let test = self.pick_test_for_match_pair(match_pair);
  	// Unwrap is ok after simplification.
  	let match_place = match_pair.place.unwrap();
  	debug!(?test, ?match_pair);
  	(match_place, test)
  	}

• similar issues
  • issue-133063
  • issue-133779

@rustbot label +F-never_patterns

[cushionbadak]

ICE is also found with other type definitions, such as struct:

#![feature(never_patterns)]
#![allow(incomplete_features)]

struct S;

fn by_value(s: S) {
    || { let ! = s; };
}

fn main() {}

[Nadrieril]

This even crashes in cases with no type error:

#![feature(never_patterns)]
#![allow(incomplete_features)]

enum Void {}

fn by_value(s: Void) {
    || { let ! = s; };
}

fn main() {}